Electric water heater for new construction

[Mark Gr]

we are buying a new construction condo (3600 sqft, 3 bedrooms/4.5 baths), and can change what we want within reason.
they are planning to install an electric 80 gallon tank (non hybrid, i assume using the light commercial exception but not sure) with recirculator in a closet. There is no basement etc since it is a condo.

Two questions:
my understanding is that after 2015 all the electric water heaters this size need to be a heat pump type, but the location is a closet so not enough space, and we dont want the noise. What happens when this tank fails? will we be stuck replacing it with a 40 gallon since we cant install the heat pump version?

or would i be better off with an electric tankless? gas is not an option

thanks for any insight.

 

[Terry]

4.5 bathrooms is a lot of hot water needed. I can see why they want to go with the 80 gallon. Heating water with electricity takes much longer. I doubt the the panel is close to having what you need to go with a tankless electric unit. With 3600 square feet there, it seems that looking into future spacing is needed. Some people are using two tanks, but even that means more power out of the box. Maybe Dana has some more of his good information he can add.

 

[Sponsor]

 

[Jadnashua]

Electric WH are certainly the easier ones to setup and configure space for, but are slow to recover. Some can be had with bigger elements, and instead of only running one, can sometimes run both at the same time (but requires much larger wiring). If possible, you get more bang for the buck with NG - generally much faster recovery. The units sometimes are available with alternate wattage elements, and you might want to specify the larger ones, which would dictate different wiring and breaker. A recirculation system helps to minimize wasting water while waiting for it to get hot at the tap, which is probably why it is specified. It has a secondary benefit in that you don't start out with that much less hot water in the tank while purging the lines. If the lines are well insulated, it's often a net gain energy wise once you take into account supplying the water, then treating the waste at the sewer.

What are you using for heating? Probably not a boiler, but if you are, ditch the electric WH and specify an indirect WH, heated by the boiler. Much faster recovery, and, most places, much cheaper than using electricity for heating things.

FWIW, a condo is a form of ownership, not indicative of the style, size, or shape of the dwelling. A condo could be a standalone house, a townhouse, a duplex, or a flat in a larger building.

 

[Dana]

we are buying a new construction condo (3600 sqft, 3 bedrooms/4.5 baths), and can change what we want within reason.
they are planning to install an electric 80 gallon tank (non hybrid, i assume using the light commercial exception but not sure) with recirculator in a closet. There is no basement etc since it is a condo.

Two questions:
my understanding is that after 2015 all the electric water heaters this size need to be a heat pump type, but the location is a closet so not enough space, and we dont want the noise. What happens when this tank fails? will we be stuck replacing it with a 40 gallon since we cant install the heat pump version?

or would i be better off with an electric tankless? gas is not an option

thanks for any insight.

I'm not sure whether CA Title 24 requires heat pump water heaters or not, but an 80 gallon ducted heat pump water heater like the Rheem Performance Platinum/ Prestige water heater can still work in a closet. (There are others.) All heat pump water heaters are a bit noisy, so plan on designing noise-abatement into the utility closet walls, ceiling and floor, and be sure to consider where the air is being drawn from or discharged to. Be generous with the access door/hatch sizing too, since these things aren't exactly small.

^^The description says "cold climate", but you can run the in & out ducts wherever you like.^^

Bear in mind that the outflow duct will be substantially cooler than room temperature, which lowers the air conditioning load, but adds to the heating load of wherever you're sending it.

With 4 full baths it's also worth adding drainwater heat recovery, assuming at least some of the baths with showers are above the first floor. It doesn't have to be co-located with the water heater to work (though that simplifies the plumbing a bit.)

The tallest and fattest that fits is the "right" one.

A drainwater heat recovery unit that's at 4" x 60" or taller will return more than half the heat that's flowing down the drain back to the incoming water stream. If that pre-heated water is fed both to the cold intake of the water heater AND the cold side of the shower mixer it will dramatically extend the apparent capacity of the water heater, at least in showering mode. It won't do anything for tub fills, since the drain and the incoming water have to be flowing simultaneously for the heat exchange to take place.

The current market leader in terms of least pressure drop and highest return efficiency is the Ecodrain V1000 series. (Renewability's PowerPipe series aren't bad either.) While these have better economic payback on water heating energy use in coldwater climates, in your case you are buying extra water heater capacity (and potentially even a smaller heat pump water heater), saving quite a bit on water heater cost to achieve the same first-hour gallons performance.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Ecodrain V1000 ^^^^^^^^^^^^^^^^^^^^^^^^

You're definitely NOT going to be better off with an electric tankless, which could become a serious financial liability as California utilities are almost certainly going to have to build in residential "demand charges" into the rate structures to pay for the grid infrastructure. (This is a whole topic in itself, but super-heavy intermittent electric loads like fast level-2 car chargers or whole-house electric tankless water heaters demand more grid infrastructure to manage when they become ubiquitous. Tankless water heater may even be banned in some locations, and car-chargers may be required to have onboard smarts to allow the utility to interrupt charging for several minutes at a time to keep the grid from burning down.)

Another approach is to go with an 83 gallon Sanden (one of the Japanese EcoCute consortium) water heater. This type of heat pump water heater uses a CO2-refrigerant heat pump in mini-split type outdoor unit, and the tank can live inside a closet. It's a pretty expensive way to go just for heating hot water (~$4K for the hardware, plus installation), but they can also be used for space heating (and cooling, but probably not for the whole 3600 square feet in CA.) The advantages here are no ducts, no noisy compressor/fan unit indoors, and a long-life stainless tank. The down side is you have to figure out where to put the outdoor unit, which is likely to be somewhat restricted by condo associations. In Japan and Australia they often put both the compressor unit and the tank outdoors, but in the US the tank usually lives indoors:

 

[Fitter30]

Ca title 24 2019 renews every three years. Looks like a 60 gallon is the largest for replacement but their also looking at minimum requirements for doors and windows. Lots of changes from 2016 to 2019. Need someone with a lot of knowledge on this subject.
https://www.globenewswire.com/Track...k3YBEe6wDgvvzaX8M8sxftUBn9R3GjkW_0YUIXTXUFbua

 

[Bannerman]

A method to obtain greater usable capacity from a smaller WH such as 40 or 60 gallons will be to increase the temperature setting.

A WH providing hot water above 120℉ will require a mixing valve. A MV will mix cold water with the higher temperature out flow to achieve 120℉ to faucets, but in doing this, less hot water will be consumed from the WH which will allow the smaller WH to provide similar usable capacity compared to a larger tank that is set at 120℉.

 

[Dana]

Y'all realize that this was a 2- years-dead thread, right?